Modern electronic devices often include electronic fuses for use in final configuration after completion of semiconductor masking and fabrication processes. These electronic fuses are typically useful in the customization of electronic devices or to correct semiconductor manufacturing defects. For example, an integrated circuit such as a processor may include multiple electronic fuses that store digital information. Each electronic fuse may store a logic 0 or logic 1 depending on whether the fuse exhibits an un-blown state or a blown-state. A programming mechanism passes a high current through a polysilicon electronic fuse to permanently change the resistance of the fuse from a low resistance of approximately 100 ohms (the un-blown state) to a high resistance of approximately 5K ohms (the blown state). This action effectively “blows the fuse”.
A “blown fuse” is an electronic fuse that exhibits high resistance after the programming mechanism passes a high current therethrough. An “un-blown fuse” is an electronic fuse that still exhibits a low resistance. The programming mechanism stores digital information in an electronic fuse bank by either blowing or not blowing individual fuses of the bank. An un-blown fuse that exhibits a low resistance may correspond to a logic low or 0. A blown fuse that exhibits a high resistance may correspond to a logic high or 1. This logic convention is reversible.
Once the programming mechanism stores digital information in the electronic fuse bank of an electronic device, the storage is permanent or nonvolatile. Nonvolatile storage of digital information is often desirable. However, circumstances arise wherein it is desirable to change or update the digital information in a nonvolatile electronic fuse bank. For example, a processor manufacturer may store final configuration information in the fuse bank of the processor. It is possible that after manufacturing a large quantity of processors and programming the fuse banks with final configuration information, an unexpected engineering change may require that the processors include different final configuration information. Under these circumstances, with no mechanism to update the final configuration information, it is unfortunately possible that those processors that store the original final configuration information may become scrap. Clearly, designating a large quantity of expensive electronic devices as scrap is not desirable.